This is the full source code of Ov source engine modification. Originally started in 2008, the development ended around 2012. All files preceeded by over_ or overlord_ are new files created for the mod. Other Source engine files have been modified.
Moddb page: http://www.moddb.com/mods/overlordess
Sample gameplay video: https://www.youtube.com/watch?v=j6sjxVfuMoY
Microsoft Visual Express 2010 is needed for compilation, use Overlord.sln. Modify project to change OutputDirectory to your desired path. If debug fails, compile in release mode.
In case of problems check Valve developer wiki first - https://developer.valvesoftware.com/wiki/Compiling_under_VS2010
Mapsrc folder contains files to use with Hammer map editor, both .vmf files and an .fgd file. Unfortunately, as of now no config for SourceSDK is available. However, when creating one make sure to use Source 2007 template and base it on HL2DM config.
Available at Moddb: http://www.moddb.com/mods/overlordess/downloads/ov-alpha-release